(1) Field of the Invention
The present invention provides a method for shaping a biodegradable, and preferably water dispersible, preform material to produce a shaped article using a heated element in a manner so as not to produce harmful fumes and residues and preferably so as not to char (blacken) the material at the cut. The present invention also relates to particular apparatus for shaping a preform material.
(2) Description of Related Art
The formation of three-dimensional objects from virtual concepts, templates or co-ordinate sets is a widely established and practiced art, existing in many diverse areas. Lathes, mills, and other machine tools use sharp metal cutters acting against metal, wood or plastic materials to create the desired objects. More recently, lasers and high pressure jets of water containing abrasives or plastic resins have extended this art for industrial applications.
Heated elements, including metal wires, blades or points have been used to cut or grove plastic materials and natural materials, such as wood as in wood burning. In addition to manual object control during the forming, applications in this field include computerized control of x, y and x, y, z axes. Many of the plastic materials release toxic fumes; particularly, volatile aromatic compounds. This necessitates operation of these devices in enclosures with sufficient venting. This problem has discouraged the extension of this art to anything other than technical applications requiring skilled users in an industrial environment. In wood burning, the surface of the wood is charred or blackened. Also, wood is not thermoplastic so it is prone to charring. In the present invention, this is not the result.
The patent arts have described the use of various heated elements for cutting preform materials to shape them. U.S. Pat. No. 2,272,931 to Boisselier describes the use of a heated wire incorporated into a hand held device to produce ornaments, figures, designs and the like. The material cut is not specified. U.S. Pat. No. 2,743,348 to Boyajean describes a tool for engraving a thermally decomposable material such as cellulose nitrate. U.S. Pat. No. 3,396,616 to Wright describes an electrically heated lance which is slidably held in place and used to perforate thermoplastic foamed plastics. The foams are not otherwise identified. U.S. Pat. No. 3,555,950 to Gijsbers et al describes the use of a heated wire to cut foils which are composed of a thermoplastic material. U.S. Pat. No. 3,902,042 to Goldfarb et al describes a tool for cutting designs in meltable materials such as styrofoam, which is a thermoplastic material. U.S. Pat. No. 4,485,295 to Kellermeyer describes an electrically heated device for cutting polystyrene or polyethylene foams. U.S. Pat. No. 4,601,224 to Clark, III describes the use of a heated wire to cut a pattern in a polyfoam. The particular material disclosed is polystyrene. U.S. Pat. No. 4,539,467 to Wenger describes the use of a heated cutting tool to cut rubber, plastic and the like. The tool is particularly adapted to cut windshield moldings. U.S. Pat. No. 4,675,825 to DeMenthon describes an automated apparatus for cutting a plastic foam, particularly styrofoam, using heated wire. U.S. Pat. No. 5,073,696 to Patillo et al describes a hand held tool with a heated tip for shaping wax used for models for making jewelry and the like. U.S. Pat. No. 5,092,208 to Rosa-Miranda describes a hot knife which is used to remove flash from molded materials. U.S. Pat. No. 5,438,758 to Roth-White describes a heated knife for cutting foods. U.S. Pat. No. 5,524,809 to Kosslow et al describes a soldering device with a retractable heated tip which could be used for cutting a preform material. U.S. Pat. No. 5,454,287 to Fuchigami et al describes a device for cutting fabrics with a thermal cutter which is indexed into position.
These prior art show that (1) a heated element can be utilized to carve, cut and shape a thermoplastic material by free-hand or by cutting a pattern inscribed on the material; (2) regulation of heat at cutting tip; (3) the use of a vacuum to remove vapors; (4) the use of multiple heated tips; (5) cutting of materials which are non-dispersible in water; (6) cutting of materials (such as polystyrene) which release harmful vapors; and (7) the charring of material such as in wood burning.
A combination of all the embodiments of the prior art results in a cutting tool that when heated can shape thermoplastic material while simultaneously releasing noxious vapors into the air and/or to char the material. The resulting shaped article is generally not easily dispersible in water.
The past ten years have seen the emergence of a new industrial technology termed free form fabrication or rapid prototyping (RP). These methods have been predominantly employed in the field of rapid tool making (RTM) to create tools and dies either directly by printing a binder onto a metal powder, followed by sintering and infiltration, or indirectly by using RP to create a pattern to form the tool by using stereolithography followed by investment casting. In outline RP uses additive processes to create a physical geometry directly from a CAD file. The predominant RP technologies include stereolithography, selective laser sintering, three-dimensional printing, fused deposition modeling, laminated object manufacturing, and the solider process. In the technique of stereolithography, fluid photosensitive resins are solidified by exposure to ultraviolet laser illumination. Selective laser sintering uses the laser-induced fusion of a polymer or polymer-coated powder. Three-dimensional printing uses an ink-jet to print binder onto a powder. Fused deposition modeling involves the extrusion of a thermoplastic material. In laminated object manufacturing, sheets of paper are cut by a laser beam. The solidar technique uses ultraviolet light to cure one layer of photosensitive resin at a time as opposed to other stereolithographic techniques that treat one point in a layer at a time. Alternative strategies presently employed to produce prototype three-dimensional models are ink-jet printing of wax or resin (rather than a binder). A typical instrument to perform these RP approaches with operating software can price from $250,000 to $1,000,000 and requires specialized handling, trained operators, and special environments to isolate the instruments. Photoreactive polymers are expensive and are generally toxic.
In an alternate approach to the rapid production of three-dimensional objects, structures are cut from a building material using a computer controlled milling device. These systems are priced between $50,000 to $100,000 and require specialized handling, skilled operators and must be used in isolated environments because of the production and release of large amounts of modeling material that are generated as fine powder. The production of such waste material can result in serious health hazards for operators.
The general market for all these object forming devices has been the prototype and tool industry. RP annual revenues are approximately $200 million with a growth rate of approximately 30 percent per year.
There are presently no technologies that are commercially available to utilize CAD/CAM tools and provide low cost RP technology and approaches to non-industrial environments. Further, there are presently no building materials available for forming objects that are non-toxic and biodegradable to make possible the introduction of RP methods into the home, school, or office/laboratory environments.
The formation of three-dimensional physical objects employing the previously described approaches to rapid prototyping depends upon the use of photoreactive resins that are exposed to ultraviolet irradiation to solidify defined regions of the material. These polymers are generally expensive, non-biodegradable, and toxic, limiting their use to controlled industrial environments. The need for a UV laser for irradiation is a further limitation on the extension of this technology to home, office or school use.
There is a need for a method for forming shaped articles where the preform material being treated is cut without harmful fumes or leaving harmful residues and preferably without charring, where the preform material and shaped article are biodegradable and preferably where the shaped article is dispersible in water. There is a need for a simpler, more reliable and economical method of providing the shaped article from the preform material.